1. Field of the Invention
The present invention relates to the cleaning of gas turbine engines and specifically to a method and apparatus which can be employed to provide thorough cleaning of a compressor of a gas turbine engine while the engine is running at or near full engine speed and load.
2. Description of the Prior Art
U.S. Pat. No. 4,065,322 issued Dec. 27, 1977, to Langford, discloses a method of removing contaminants from a gas turbine engine, such as an aircraft gas turbine engine. The patent removes contaminants from vanes and blades associated with the compressor of an aircraft gas turbine engine of the high by-pass type. The patent notes that in service, the surfaces of the compressor blades and vanes become coated with contaminants of various types. Oil and dirt have been found to adhere to the blade and vane surfaces. Aluminum and other metal substances erode from other portions of the engine and are deposited on the blades and vanes. As discussed in the patent, while one can remove contaminants from the engine by disassembly, it is much more desirable to remove the contaminants while the engine is in use and without interfering with the structural and metallurgical integrity of other components of the engine.
The Langford patent notes that liquid solvents have been proposed to be ingested in the engine with the engine set at idle speeds. The patent states, however, that liquid solvents chemically attack not only the contaminants, but other portions of the engine which are made of the same material as the contaminants. The patent states that ingestion of liquid solvents into the engine is not proven to be an acceptable method of removing the contaminants. The patent also discusses the use of solid particle abrasives ingested into the engine at idle speeds, but notes that such methods have been unsatisfactory for a variety of reasons.
The method of the patent proposes to use abrasive particles of coke having a carbon content of at least 80% by weight and a volatile matter content of less than 6% by weight and entraining the abrasive particles in the fluid flow stream, and directing the fluid flow stream in impingement onto the contaminated surface.
U.S. Pat. No. 4,196,020 to Hornak et al., cleans a gas turbine engine while the engine is being cranked. The patent employs an apparatus consisting of a manifold assembly releasably connected to the leading edge of the engine, which assembly includes an array of spray nozzles. The spray nozzles are located at specific locations within the engine relative to radially extending struts and each nozzle has an elongated spray pattern, the longitudinal axis of which is generally perpendicular to a radius of the engine inlet. The patentees claim that the sprays eminating from the nozzle within the inlet achieve the desired overlapping wash spray and are effective to completely wash the entire length of the adjacent strut-structures disposed in the engine inlet. The fluid applied to the engine is described as being a cleaning fluid and a rinsing fluid or a preservative fluid.